U.S. patent application number 11/723377 was filed with the patent office on 2008-05-01 for light guide for use in a keypad.
This patent application is currently assigned to Lite-On Technology Corporation. Invention is credited to Kun-Neng Lee, Yi-Hsiang Tseng.
Application Number | 20080101083 11/723377 |
Document ID | / |
Family ID | 39329875 |
Filed Date | 2008-05-01 |
United States Patent
Application |
20080101083 |
Kind Code |
A1 |
Lee; Kun-Neng ; et
al. |
May 1, 2008 |
Light guide for use in a keypad
Abstract
A light guide for a keypad includes a plurality of through hole
portions adapted to correspond respectively to keys on the keypad.
Each of the through hole portions is adapted to receive at least a
part of the corresponding key, and to receive light incident
thereinto from at least one light source. Each of selected ones of
the through hole portions has a contour with a non-curved contour
portion that includes a light incident face and a reflecting face
forming an angle with the light incident face. Light incident on
the reflecting face is reflected into at least one other through
hole portion. The light guide can also be configured to have a
tree-like structure.
Inventors: |
Lee; Kun-Neng; (Taipei,
TW) ; Tseng; Yi-Hsiang; (Taipei, TW) |
Correspondence
Address: |
ROSENBERG, KLEIN & LEE
3458 ELLICOTT CENTER DRIVE-SUITE 101
ELLICOTT CITY
MD
21043
US
|
Assignee: |
Lite-On Technology
Corporation
|
Family ID: |
39329875 |
Appl. No.: |
11/723377 |
Filed: |
March 16, 2007 |
Current U.S.
Class: |
362/610 |
Current CPC
Class: |
G02B 6/0018 20130101;
G02B 6/0021 20130101 |
Class at
Publication: |
362/610 |
International
Class: |
F21V 7/04 20060101
F21V007/04 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 27, 2006 |
TW |
095219036 |
Claims
1. A light guide adapted for use in a keypad, comprising: a
plurality of through hole portions adapted to correspond
respectively to keys on the keypad, each of said through hole
portions being adapted to receive at least a part of the
corresponding key and to receive light incident thereinto from at
least one light source, wherein each of selected ones of said
through hole portions has a contour with a non-curved contour
portion, said non-curved contour portion including at least one
light incident face and at least one reflecting face that forms an
angle with said light incident face, light incident on said
reflecting face being reflected to at least one other of said
through hole portions.
2. The light guide according to claim 1, wherein said light guide
defines a proximate end and a distal end, the light source being
disposed adjacent to said proximate end, said light incident faces
slanting toward said proximate end, each of said light incident
faces being arranged such that an angle of incidence of light
emitted from the light source and directly incident thereon is
smaller than a critical angle of total internal reflection thereof,
each of said reflecting faces being arranged such that an angle of
incidence of light emitted from the light source and directly
incident thereon is larger than a critical angle of total internal
reflection thereof.
3. The light guide according to claim 2, wherein said light guide
is formed from polycarbonate.
4. The light guide according to claim 2, wherein said light guide
is formed from polymethyl methacrylate.
5. The light guide according to claim 2, wherein said light
incident face is perpendicular to a line interconnecting a center
of the respective one of said through hole portions and the light
source.
6. The light guide according to claim 2, wherein said light
incident faces increase in size from said proximate end to said
distal end.
7. The light guide according to claim 2, wherein said reflecting
faces decrease in size from said proximate end to said distal
end.
8. The light guide according to claim 2, wherein said selected ones
of said through hole portions are polygonal in shape.
9. The light guide according to claim 2, wherein said through hole
portions are arranged in three rows extending from said proximate
end to said distal end, and including a left row, a right row, and
a middle row between said left and right rows.
10. The light guide according to claim 9, wherein said through hole
portions in the middle row have symmetrical left and right sides,
the contour of each of said selected ones of said through hole
portions which is in the middle row having two of said light
incident faces and two of said reflecting faces.
11. The light guide according to claim 10, wherein said two
reflecting faces of each of said selected ones of said through hole
portions in the middle row are oriented toward the left and right
rows, respectively.
12. The light guide according to claim 9, wherein the contour of
each of said selected ones of said through hole portions which is
in one of the left and right rows has one of said light incident
faces, and one of said reflecting faces, said one of said
reflecting faces being oriented toward the middle row.
13. The light guide according to claim 9, further comprising two
triangular through hole portions that are disposed adjacent to said
distal end, wherein one of said triangular through hole portions is
disposed between the left and middle rows, and another one of said
triangular through hole portions is disposed between the right and
middle rows, each of said triangular through hole portions
including two of said reflecting faces, said two of said reflecting
faces slanting toward said proximate end.
14. A light guide for use in a keypad and substantially having a
tree structure, said light guide comprising: at least one primary
passage portion having a proximate end and a distal end such that
light emitted from at least one light source disposed adjacent to
said proximate end is transmitted through said primary passage
portion to said distal end; a plurality of secondary passage
portions branching from two opposite sides of said primary passage
portion in a spaced-apart relationship so as to permit entry of
light in said primary passage portion thereinto such that the light
can travel to distal ends of said secondary passage portions; and a
plurality of through hole portions disposed respectively at said
distal ends of said secondary passage portions and being adapted to
correspond respectively to keys on the keypad, each of said through
hole portions being adapted to receive at least a part of the
corresponding key, light in each of said secondary passage portions
being incident into the corresponding one of said through hole
portions.
15. The light guide according to claim 14, wherein said secondary
passage portions which are adjacent to said proximate end are
narrower than said secondary passage portions which are distal from
said proximate end.
16. The light guide according to claim 14, wherein said secondary
passage portions extend obliquely toward said distal end.
17. The light guide according to claim 14, wherein each of said
through hole portions includes an annular passage communicated with
the respective one of said secondary passage portions, and a
cylindrical through hole surrounded and defined by said annular
passage, light in each of said secondary passage portions entering
into said annular passage of the respective one of said through
hole portions.
18. The light guide according to claim 17, wherein each of said
annular passages has an inner annular peripheral surface and an
outer annular peripheral surface, the light incident into said
annular passage undergoing multiple reflections between said inner
and outer annular peripheral surfaces, light incident on said inner
annular peripheral surface being partly refracted thereby into said
cylindrical through hole.
19. The light guide according to claim 17, further comprising a
plurality of auxiliary passage portions intercommunicating a
corresponding adjacent pair of said annular passages.
20. The light guide according to claim 19, wherein each of said
auxiliary passage portions has a width that decreases from said
proximate end to said distal end.
21. The light guide according to claim 14, comprising two of said
primary passage portions that are parallel to each other.
22. The light guide according to claim 21, further comprising two
transverse passage portions extending perpendicularly and
respectively from said distal ends of said primary passage portions
in opposite directions, and two through hole portions disposed at
distal ends of said two transverse passage portions, respectively,
each of said through hole portions being adapted to correspond to a
key on the keypad and to receive at least a part of the
corresponding key, an oblique face being formed at a juncture
between each of said primary passage portions and the corresponding
one of said transverse passage portions for reflecting light to
enter the corresponding one of said transverse passage
portions.
23. The light guide according to claim 14, wherein said at least
one primary passage portion has a width that decreases from said
proximate end to said distal end.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority of Taiwanese Application
No. 095219036, filed on Oct. 27, 2006.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates to a light guide, more particularly to
a light guide for use in a keypad.
[0004] 2. Description of the Related Art
[0005] Referring to FIG. 1, R.O.C. Utility Model Publication No.
266654 discloses a light guide 1 for a mobile phone keypad. The
light guide 1 is used in combination with a light emitting diode
(LED) 19 disposed proximate to a lateral edge of the light guide 1
such that keys (not shown) on a keypad disposed on an upper side of
the light guide 1 are illuminated.
[0006] Light emitted from the LED 19 is reflected by peripheral
walls 111 defining a plurality of holes 11 before it is incident
into a hole 12 which is farthest from the LED 19. However, when the
light is incident on a spot of the peripheral wall 111, some of the
light is reflected thereby while the rest passes therethrough into
the hole 11. Therefore, if the light is reflected by the peripheral
walls 111 of a greater number of holes 11, the intensity of the
light will be weakened, so that the intensity of the light incident
into the hole 12 farthest from the LED 19 is weakest. Since the
peripheral wall 111 of each hole 11 in the light guide 1 functions
to both admit light and reflect light at every spot, and is not
provided with any particular proportion of light admission to light
reflection, and since there is not any special design with respect
to the angle of incident light, light emitted from the LED 19
cannot reach the hole 12 farthest from the LED 19 directly or
through a single reflection, thereby resulting in a weaker
intensity of the light in the hole 12 farthest from the LED 19, and
non-uniform distribution of light among the holes 11, 12. Thus, the
brightness of the light illuminating the keys on the keypad is
inconsistent.
SUMMARY OF THE INVENTION
[0007] Accordingly, the object of the present invention is to
provide a light guide that permits uniform illumination of all the
keys on a keypad while using a small number of light sources.
[0008] The light guide for use in a keypad of this invention
includes a plurality of through hole portions, in which each of
selected ones of the through hole portions has a contour with a
non-curved contour portion. A portion of light incident on the
non-curved contour portion of one through hole portion is reflected
to at least one other through hole portion. The non-curved contour
portion is preferably a linear segment.
[0009] Accordingly, the light guide for use in a keypad of this
invention includes a plurality of through hole portions adapted to
correspond respectively to keys on the keypad, each of the through
hole portions being adapted to receive at least a part of the
corresponding key. The light guide defines a proximate end and a
distal end. The through hole portions are arranged in three rows
extending from the proximate end to the distal end along a
respective row line, and including a left row, a right row, and a
middle row between the left and right rows. Two light sources are
disposed adjacent to the proximate end, with one light source
disposed between the row lines of the left and middle rows, and the
other disposed between the row lines of the middle and right rows.
Light emitted from the two light sources is incident into each of
the through hole portions. Each of selected ones of the through
hole portions has a contour with a non-curved contour portion. A
portion of the light incident on the non-curved contour portion is
reflected to at least one other through hole portion.
[0010] The contour of each selected one of the through hole
portions includes at least one light incident face slanting toward
the proximate end, and at least one reflecting face forming an
angle with the light incident face. The light incident faces
increase in size from the proximate end to the distal end, whereas
the reflecting faces decrease in size from the proximate end to the
distal end. Light incident on the light incident face is refracted
into the corresponding through hole portion. Light incident on the
reflecting face is reflected thereby into the other through hole
portions.
[0011] Since one of the light sources is disposed between the row
lines of the left and middle rows and the other of the light
sources is disposed between the row lines of the middle and right
rows, most of the through hole portions of the light guide receive
light directly incident thereinto from the light sources. The rest
receive light that is reflected by the reflecting face of one
through hole portion. Therefore, more light can enter into the
through hole portions that are adjacent to the distal end.
[0012] Accordingly, the light guide for use in a keypad may have a
substantially tree-like structure, and includes at least one
primary passage portion, a plurality of secondary passage portions,
and a plurality of through hole portions.
[0013] The primary passage portion has a proximate end and a distal
end such that light emitted from at least one light source disposed
adjacent to the proximate end is transmitted through the primary
passage portion to the distal end. Each of the secondary passage
portions branches from two opposite sides of the primary passage
portion in a spaced-apart relationship, and the secondary passage
portions which are adjacent to the proximate end are narrower than
the secondary passage portions which are distal from the proximate
end. The secondary passage portions permit entry of light in the
primary passage portion thereinto such that the light can travel to
distal ends of the secondary passage portions. Each of the through
hole portions is disposed at the distal end of a respective
secondary passage portion, and is adapted to correspond to a key on
the keypad. Each of the through hole portions is adapted to receive
at least a part of the corresponding key. Light in the secondary
passage portions is incident into the corresponding through hole
portions.
[0014] In the present invention, since the light incident faces of
the through hole portions in the first embodiment of the light
guide increase in size from the proximate end of the light guide to
the distal end thereof, since the reflecting faces of the through
hole portions decrease in size from the proximate end of the light
guide to the distal end thereof, and since the secondary passage
portions in the second embodiment of the light guide are narrower
near the proximate end of the primary passage portion than those
near the distal end thereof, excess light from the light sources
can be prevented from entering the through hole portions near the
proximate end of the light guide to ensure that there is sufficient
light entering the through hole portions near the distal end of the
light guide.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Other features and advantages of the present invention will
become apparent in the following detailed description of the
preferred embodiments with reference to the accompanying drawings,
of which:
[0016] FIG. 1 is a top view to illustrate a conventional light
guide for use in a keypad of a mobile phone;
[0017] FIG. 2 is a top view to illustrate the first preferred
embodiment of a light guide for use in a keypad according to the
present invention;
[0018] FIG. 3 is a sectional side view to illustrate the
relationship of the first preferred embodiment with other
components of a mobile phone employing the first preferred
embodiment;
[0019] FIG. 4 is a schematic view to illustrate how a reflecting
face of a polygonal through hole portion of the first preferred
embodiment is determined;
[0020] FIG. 5 is a top view to illustrate the second preferred
embodiment of a light guide for use in a keypad according to the
present invention; and
[0021] FIG. 6 is a top view to illustrate the transmission of light
from two LEDs into first and second through hole portions of the
light guide of the second preferred embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] Referring to FIG. 2, the first preferred embodiment of a
light guide 300 for use in a keypad according to the present
invention is adapted for illuminating keys on a keypad of an
electronic device, such as a mobile phone. FIG. 3 illustrates an
example of the positional relationship between the light guide 300
and other components of the mobile phone. As shown, a circuit board
21 is provided with a plurality of metal domes 22 (only one is
shown) and a polyethylene terephthalate (PET) film 23. An
electrical connection is established between the metal dome 22 and
the circuit board 21 upon pressing of the metal dome 22. The light
guide 300 is disposed on the PET film 23. Two light emitting diodes
(LED) 24 (only one is shown in FIG. 3) are disposed proximate to
one end of the light guide 300. Light emitted from each LED 24 is
incident into the light guide 300 from a lateral part of the light
guide 300. A silicone rubber pad 25, a light shielding sheet 26,
and a keypad having a plurality of keys 27 (only one is shown in
FIG. 3) are disposed in sequence on an upper side of the light
guide 300.
[0023] Referring to FIG. 2 and FIG. 3, the light guide 300 includes
a plurality of polygonal through hole portions 31, 32, a plurality
of cylindrical through hole portions 41, and two triangular through
hole portions 421, 422.
[0024] The light guide 300 defines a proximate end 431 and a distal
end 432. Each of the polygonal through hole portions 31, 32 and the
cylindrical through hole portions 41 corresponds to one of the keys
27, and receives at least a portion of the corresponding key 27.
The polygonal through hole portions 31, 32 and the cylindrical
through hole portions 41 are arranged in three rows: a left row
441, a right row 443, and a middle row 442 between the left and
right rows 441, 443. Each row 441, 442, 443 extends from the
proximate end 431 to the distal end 432 along a respective row
line. The positions of the keys 27 and their corresponding through
hole portions 31, 32, 41 can be adjusted according to different
mobile phone models. For example, in this embodiment, the two
through hole portions 41 in the left and right rows 441, 443
closest to the proximate end 431 are cylindrical while the other
ten through hole portions 31, 32 adjacent to the proximate end 431
are polygonal. It is noted that the cylindrical through hole
portions 41 can be configured to be polygonal in shape in other
embodiments of this invention.
[0025] Each of the polygonal through hole portions 31 in the left
and right rows 441, 443 has a contour with a light incident face
311 slanting toward the proximate end 431, and a reflecting face
312 forming an angle with the light incident face 311 and oriented
toward the middle row 442. Each of the polygonal through hole
portions 32 in the middle row 442 is a regular polygon with
symmetrical left and right sides, and has a contour with two light
incident faces 321 that slant toward the proximate end 431, and two
reflecting faces 322 each of which is contiguous to and forms an
angle with a corresponding one of the light incident faces 321. The
two reflecting faces 322 of each of the polygonal through hole
portions 32 in the middle row 442 are oriented to the left and
right rows 441, 443, respectively. In addition, the light incident
faces 311, 321 increase in size from the proximate end 431 to the
distal end 432, whereas the reflecting faces 312, 322 decrease in
size from the proximate end 431 to the distal end 432.
[0026] It is noted that the through hole portions 31, 32 may not be
polygonal in shape, and may instead have a non-curved contour
portion such that the through hole portions 31, 32 have the
aforesaid light incident faces 311, 321 and the reflecting faces
312, 322 at the required positions. In this case, the rest of the
contour of the through hole portions 31, 32 may be curved.
[0027] The two triangular through hole portions 421, 422 are
disposed adjacent to the distal end 432, with one located between
the left row 441 and the middle row 442, and the other located
between the middle row 442 and the right row 443. One of the
triangular through hole portions 421 includes two reflecting faces
423, 424 that slant toward the proximate end 431. The other of the
triangular through hole portions 422 likewise has two reflecting
faces 425, 426 that slant toward the proximate end 431. As the
triangular through hole portions 421, 422 are provided to reflect
light for light guiding purposes, keys are not provided to
correspond thereto.
[0028] Two LED receiving holes 45 are formed in the lateral part of
the light guide 300 at corresponding positions for respectively
receiving the LEDs 24, such that one of the LEDs 24 is located
among the proximate end 431 and the through hole portions 41, 32 in
the left and middle rows 441, 442 (i.e., between the row lines of
the left and middle rows 441, 442), while the other of the LEDs 24
is located among the proximate end 431 and the through hole
portions 32, 41 in the middle and right rows 442, 443 (i.e.,
between the row lines of the middle and right rows 442, 443). On
the other hand, the LED receiving holes 45 may be omitted, and the
LEDs 24 are disposed to confront a lateral edge of the light guide
300 adjacent to the proximate end 431 in other embodiments of the
invention. Moreover, more LEDs 24 can be provided, and are
preferably positioned symmetrically.
[0029] Light emitted from the LEDs 24 are respectively incident
into the through hole portions 31, 32, 41, 421, 422. The
arrangement of the light incident faces 311, 321 of the polygonal
through hole portions 31, 32 is such that an angle of incidence of
light emitted from the corresponding LED 24 and incident directly
on the light incident face 311, 321 is smaller than a critical
angle of total internal reflection of the light incident face 311,
321, so that some of the energy of the light incident on the light
incident face 311, 321 can be refracted into the corresponding
polygonal through hole portion 31, 32. On the other hand, the
arrangement of the reflecting faces 312, 322 of the polygonal
through hole portions 31, 32 is such that an angle of incidence of
light emitted from the corresponding LED 24 and incident directly
on the reflecting face 312, 322 is larger than a critical angle of
total internal reflection of the reflecting face 312, 322, so that
the light incident on the reflecting face 312, 322 can be reflected
completely due to total internal reflection, and can be preferably
reflected onto the light incident faces 311, 321 of the other
polygonal through hole portions 31, 32 or into the cylindrical
through hole portions 41.
[0030] In this embodiment, the light guide 300 is formed from
polycarbonate (PC), polymethyl methacrylate (PMMA, commonly known
as acrylic), or other suitable light-transmissive materials. If the
light guide 300 is formed from a PC material, the refractive index
of the light guide 300 is 1.584. Therefore, the critical angles of
total internal reflection of the light incident faces 311, 321 and
the reflecting faces 312, 322 are all equal to 39 degrees. If the
light guide 300 is formed from PMMA, the refractive index of the
light guide 300 is 1.492. Therefore, the critical angles of total
internal reflection of the light incident faces 311, 321 and the
reflecting faces 312, 322 are all equal to 42 degrees.
[0031] In this embodiment, due to the layout of the keys 27, the
cylindrical through hole portions 41 which are closest to the
distal end 432 in the left and right rows 441, 443 are partly
blocked by the cylindrical through hole portion 41 closest thereto
in the same row, so that there is not sufficient light incident
thereinto. Thus, the arrangement of the reflecting faces 423, 426
of the triangular through hole portions 421, 422 help reflect the
light to the cylindrical through hole portions 41 which are closest
to the distal end 432 in the left and right rows 441, 443.
Moreover, the angles of the reflecting faces 423, 426 are such that
total internal reflection can occur. However, if the layout of the
keys 27 is such that the cylindrical through hole portions 41 which
are closest to the distal end 432 in the left and right rows 441,
443 are not blocked, a preferred state can be had. That is, the
light emitted from the LEDs 24 can be directly incident into the
cylindrical through hole portions 41 closest to the distal end 432,
or the light can be incident thereinto through a single reflection,
thereby dispensing with the need to provide the triangular through
hole portions 421, 422.
[0032] Therefore, preferably, all the polygonal through hole
portions 31, 32 and the cylindrical through hole portions 41 at
least receive once-reflected light from the LEDs 24. Some may even
have light directly incident thereinto. Therefore, even the
cylindrical through hole portions 41 closest to the distal end 432
may still have sufficient light incident thereinto. In other words,
all of the polygonal through hole portions 31, 32 and the
cylindrical through hole portions 41 will have sufficient light
incident thereinto.
[0033] Furthermore, since the light incident faces 311, 321 of the
polygonal through hole portions 31, 32 in the left, middle and
right rows 441, 442, 443 increase in size from the proximate end
431 to the distal end 432, and since the reflecting faces 312, 322
in the left, middle and right rows 441, 442, 443 decrease in size
from the proximate end 431 to the distal end 432, there will not be
too much light going into the polygonal through hole portions 31,
32 near the proximate end 431 by way of the light incident faces
311, 321. Besides, since the reflecting faces 312, 322 near the
proximate end 431 are sufficiently large, there will be a
sufficient amount of light reflected into the through hole portions
31, 32, 41 near the distal end 432. Conversely, since the light
incident faces 311, 321 near the distal end 432 are relatively
larger, a larger amount of light, whose energy has become weak, can
be incident thereon. Thus, the intensities of light incident into
all the through hole portions 31, 32, 41 can be relatively uniform
to permit uniform illumination of all the keys 27 on the
keypad.
[0034] When designing the shapes of the polygonal through hole
portions 31, 32, optical simulation software is used to obtain
optimum shapes thereof. First, cylindrical through hole portions
are disposed in positions corresponding to the keys 27 of a certain
model of mobile phone. Then, the cylindrical through hole portions
in the middle row 442 and closer to the proximate end 431 are
modified into the polygonal through hole portions 32 having two
light incident faces 321 and two reflecting faces 322.
[0035] The two light incident faces 321 are respectively oriented
toward the LEDs 24. Of the light beams emitted from each LED 24,
there will be a light beam passing through the center of the
polygonal through hole portion 32. This light beam can be regarded
as a line interconnecting the center of the polygonal through hole
portion 32 and the LED 24. The face perpendicular to the
interconnecting line is then selected as the light incident face
321 so that the angles of incidence of light beams incident on the
light incident face 321 are preferably small angles, and are
smaller than the critical angle of total internal reflection of the
light incident face 321.
[0036] The determination of the reflecting faces 322 will now be
illustrated using the reflecting face 322 on the left side of the
polygonal through hole portion 32, and with further reference to
FIG. 4. Straight lines (L1), (L2) can be drawn to connect the
center of the polygonal through hole portion 32 to the LED 24 on
the left side thereof and to the center of a selected through hole
portion 31 (basically, the through hole portion closest to the
distal end 432 is selected). A line (L3) bisecting an angle formed
between the lines (L1) and (L2) is a line normal to the reflecting
face 322 to be determined, and the face perpendicular to the normal
line (the bisecting line L3) is selected as the reflecting face
322. However, if the angle of incidence of light directly incident
on the selected reflecting face 322 is not larger than the critical
angle of total internal reflection of the selected reflecting face
322, the angle of the reflecting face 322 can be fine-tuned such
that the angle of incidence of light directly incident on the
selected reflecting face 322 is larger than the critical angle of
total internal reflection of the selected reflecting face 322.
[0037] Referring once again to FIG. 2, the sizes of the light
incident faces 311, 321, and the reflecting faces 312, 322 are
determined by the intensity of light that is required to be
incident into the corresponding polygonal through hole portions 31,
32 and the intensity of light that is required to be reflected.
Likewise, the optimum shapes for the other polygonal through hole
portions 31, 32 are determined using optical simulation described
hereinabove. During the simulation process, the determined light
incident faces 311, 321 and reflecting faces 312, 322 can be
fine-tuned to match the light incident faces 311, 321 and
reflecting faces 312, 322 that are yet to be determined so that the
intensity of light incident into the through hole portions 31, 32,
41 can be made uniform.
[0038] Referring to FIG. 5, the second preferred embodiment of a
light guide 500 for use in a keypad according to the present
invention is shown to have a substantially tree-like structure. The
light guide 500 includes two primary passage portions 51, a
plurality of secondary passage portions 52, a plurality of first
through hole portions 6, a plurality of auxiliary passage portions
53, two transverse passage portions 54, two second through hole
portions 7, and five third through hole portions 55.
[0039] The two primary passage portions 51 are parallel to each
other. Each primary passage portion 51 includes a proximate end 511
and a distal end 512. Each primary passage portion 51 has a width
that decreases from the proximate end 511 to the distal end 512.
The secondary passage portions 52 are disposed to branch from two
opposite sides of a respective one of the primary passage portions
51 in a spaced-apart relationship, and extend obliquely toward the
distal end 512 of the respective one of the primary passage
portions 51. Furthermore, the secondary passage portions 52
adjacent to the proximate end 511 of the respective primary passage
portion 51 are narrower than the secondary passage portions 52
distal from the proximate end 511 of the respective primary passage
portion 51.
[0040] The first through hole portions 6 are disposed at distal
ends of corresponding ones of the secondary passage portions 52.
Each of the first through hole portions 6 is adapted to correspond
to a key (not shown) on the keypad. In this embodiment, the first
through hole portions 6 are arranged in three rows. Each of the
first through hole portions 6 in the middle row is disposed at the
distal ends of two associated secondary passage portions 52
branching respectively from the primary passage portions 51, one
being the secondary passage portion 52 extending obliquely
rightward from the primary passage portion 51 on the left, the
other being the secondary passage portion 52 extending obliquely
leftward from the primary passage portion 51 on the right. Each of
the first through hole portions 6 in the left and right rows is
disposed at the distal end of the respective one of the secondary
passage portions 52. Each of the first through hole portions 6
includes an annular passage 61 communicated with the corresponding
secondary passage portion 52, and a cylindrical through hole 62
surrounded and defined by the annular passage 61. The cylindrical
through hole 62 is adapted to receive at least a part of the
corresponding key on the keypad. Each annular passage 61 has an
inner annular peripheral surface 611 and an outer annular
peripheral surface 612.
[0041] Each of the auxiliary passage portions 53 intercommunicates
some of the annular passages 61 in pairs, and has a width that
decreases from the proximate end 511 of the respective primary
passage portion 51 to the distal end 512 thereof. The two
transverse passage portions 54 extend perpendicularly and
respectively from the distal ends 512 of the primary passage
portions 51. The two second through hole portions 7 are
respectively disposed at distal ends of the two transverse passage
portions 54, and are adapted to correspond respectively to two keys
(not shown) on the keypad. Each of the second through hole portions
7 includes an annular passage 71 communicated with the
corresponding transverse passage portion 54, and a cylindrical
through hole 72 surrounded and defined by the annular passage 71.
The cylindrical through hole 72 is adapted to receive at least a
part of the corresponding key. Each annular passage 71 likewise has
an inner annular peripheral surface 711 and an outer annular
peripheral surface 712. Besides, an oblique face 541 is formed at a
juncture between each of the primary passage portions 51 and the
corresponding transverse passage portion 54.
[0042] The five third through hole portions 55 are arranged in a
cross shape, and are generally provided to correspond to navigation
and confirmation keys (not shown) on the keypad. As the navigation
and confirmation keys can be correctly pressed without even
looking, the third through hole portions 55 need not be
illuminated. In this case, to maintain structural integrity of the
light guide 500, it only requires relatively thin interconnections
between adjacent ones of the third through hole portions 55, as
well as with the primary passage portions 51 and the second through
hole portions 7 associated therewith. Such interconnections are not
required to have a light guiding function.
[0043] Referring to FIG. 6, two LEDs 24 are respectively disposed
adjacent to the proximate ends 511 of the two primary passage
portions 51. A portion of the light emitted from each LED 24 is
transmitted along the respective primary passage portion 51 to the
distal end 512 thereof, where the light is reflected by the oblique
face 541 to travel into the annular passage 71 of the respective
second through hole 7 via the respective transverse passage portion
54. The rest of the light traveling in each primary passage portion
51 is incident into the annular passages 61 of the corresponding
first through hole portions 6 via the secondary passage portions
52. The light incident into the respective annular passages 61, 71
will undergo multiple reflections between the inner and outer
annular peripheral surfaces 611, 612, 711, 712. Every time there is
light incident on the inner annular peripheral surface 611, 711, a
portion of the light will be refracted into the corresponding
cylindrical through hole 62, 72. Therefore, light goes into the
cylindrical through holes 62, 72 from different directions, thereby
resulting in uniform distribution of light intensities within the
cylindrical through holes 62, 72.
[0044] In addition, the arrangement of the auxiliary passage
portions 53 helps guide a portion of the light within the annular
passage 61 in an interconnected pair of the annular passages 61
which is closer to the proximate end 511 to the annular passage 61
of the interconnected pair which is closer to the distal end 512
such that the annular passages 61 farther from the proximate ends
511 of the primary passage portions 51 also have sufficient
incident light. The arrangement of a diminishing width of the
auxiliary passage portions 53 from the proximate end 511 to the
distal end 512 can prevent light in the annular passages 61 farther
from the proximate end 511 from entering into the respective
auxiliary passage portions 53 that tends to weaken the light
intensity.
[0045] Furthermore, if each of the primary passage portions 51 was
configured to have a uniform width from the proximate end 511 to
the distal end 512 thereof, there would be excess light directly
incident into the distal end 512 thereof, which would result in
over-brightness in the second through hole portions 7 and
insufficient brightness in the first through hole portions 6 near
the distal end 512. Therefore, the width of each primary passage
portion 51 in this embodiment is configured to decrease from the
proximate end 511 to the distal end 512, so as to avoid direct
incidence of excess light into the distal end 512 of the respective
primary passage portion 51.
[0046] Since the light intensity at the proximate ends 511 of the
primary passage portions 51 is relatively strong, the width of the
secondary passage portions 52 near the proximate ends 511 of the
primary passage portions 51 is not required to be too large, so
that there will be sufficient light entering the first through hole
portions 6 near the proximate ends 511. However, with the light
dispersing into the secondary passage portions 52 along the primary
passage portions 51, the light at the distal ends 512 is relatively
weak. Therefore, the width of the secondary passage portions 52
adjacent to the distal ends 512 is relatively large to ensure entry
of sufficient light into the secondary passage portions 52. Thus,
this embodiment can also achieve relatively uniform intensities of
light incident into the first and second through hole portions 6, 7
to result in uniform illumination of the keys on the keypad.
[0047] In sum, the light guide 300, 500 for use in a keypad
according to the present invention controls the proportion of
incident light and/or reflected light by varying the sizes of the
light incident faces 311, 321 and the reflecting faces 312, 322, or
by varying the widths of the primary passage portions 51 and the
secondary passage portions 52 according to the positions thereof.
Thus, there will not be excess light entering into the through hole
portions 31, 32, 41, 6 that are near the proximate ends 431, 511,
and there will be sufficient light to be reflected or guided into
the through hole portions 31, 32, 41, 6, 7 that are near the distal
ends 432, 512. Furthermore, the polygonal through hole portions 31,
32 and the cylindrical through hole portions 41 in the first
preferred embodiment will receive light that is only once-reflected
after issuing from the LED 24, thereby ensuring incidence of
sufficient light thereinto. Consequently, the light guide 300, 500
merely requires two LEDs 24 to achieve uniform illumination of the
keys on the keypad.
[0048] While the present invention has been described in connection
with what are considered the most practical and preferred
embodiments, it is understood that this invention is not limited to
the disclosed embodiments but is intended to cover various
arrangements included within the spirit and scope of the broadest
interpretation so as to encompass all such modifications and
equivalent arrangements.
* * * * *